Let's see ~ a list of things that might make a book delightful: under 150 pages long (check), illustrations (check), George Washington (check), snow! (check), Christmas (check), Valley Forge (check!).
With a list like this, S. Weir Mitchell's A Venture in 1777 can't help but be satisfying!
Okay, so the story isn't all that much. Young Tom Markham and his twin brothers (but mostly Tom) conspire to steal an important military secret from Colonel Grimstone and relay it to Valley Forge just after Christmas. Their house is occupied by the British and they'd like very much to get rid of their unwanted guests ~ and get their father back (he is currently a prisoner of war).
Mitchell apparently enjoyed writing "historical" fiction and has a number of books set during the American Revolution and Washington's term as President. This particular little tome, he wrote for charity with the proceeds going to the Philadelphia Church Home for Children. The book isn't terribly fancy, but it does have some nice vignettes and illustrations (spot colored in cyan). The artist, unfortunately is uncredited, but you can see what nice work was done in the image below.
Near as I can tell, the story is entirely fictional outside of the circumstances of the war. General Washington would appear to be the only "real-life" character. I've haven't yet read any of Mitchell's Revolutionary War novels, so I don't know whether he's predisposed to adhere to much fact. His Civil War novels are certainly grounded in fact, but the historical people who appear in them generally pop in and out of scenes rather quick (much like Washington in this one).
By the way: Two amusing things about the illustration above: Tom is fifteen (nearly sixteen). In the picture he looks more like twelve! Also, do you really think Washington wore stockings at Valley Forge? Much as I like the picture, the shoes, I had to laugh at.